Abstract
Perpendicularly magnetized tunnel junctions (p-MTJs) show promise as reliable candidates for next-generation memory due to their outstanding features. However, several key challenges remain that affect CoFeB/MgO-based p-MTJ performance. One significant issue is the low thermal stability (Δ) due to the rapid perpendicular magnetic anisotropy (PMA) degradation during annealing at temperatures greater than 300 °C. Thus, the ability to provide thermally robust PMA characteristics is a key steps towards extending the use of these materials. Here, we examine the influence of a W spacer on double MgO/CoFeB/W/CoFeB/MgO frames as a generic alternative layer to ensure thermally-robust PMAs at temperatures up to 425 °C. The thickness-dependent magnetic features of the W layer were evaluated at various annealing temperatures to confirm the presence of strong ferromagnetic interlayer coupling at an optimized 0.55 nm W spacer thickness. Using this W layer we achieved a higher Δ of 78 for an approximately circular 20 nm diameter free layer device.
Highlights
Magnetized tunnel junctions (p-magnetic tunnel junctions (MTJs)) show promise as reliable candidates for nextgeneration memory due to their outstanding features
Samples A and B are denoted as single-CoFeB frames with W buffers and capping layers, respectively, and Sample C is denoted as a double-CoFeB frame
Two different stacks containing a Ta or W metal spacer in a double-CoFeB frame were prepared for comparison
Summary
Magnetized tunnel junctions (p-MTJs) show promise as reliable candidates for nextgeneration memory due to their outstanding features. The thickness-dependent magnetic features of the W layer were evaluated at various annealing temperatures to confirm the presence of strong ferromagnetic interlayer coupling at an optimized 0.55 nm W spacer thickness Using this W layer we achieved a higher Δ of 78 for an approximately circular 20 nm diameter free layer device. P-MTJs based on CoFeB/MgO frames show promise as reliable building blocks due to their high tunneling magnetoresistance (TMR) ratio[10] These materials still have the disadvantage of a low thermal stability, which can be expressed as Δ = EB/kBT = KeffV/kBT. We report the effects of W spacers on double MgO/CoFeB/W/CoFeB/MgO frames These structures exhibited thermal stability even at a high annealing temperature of 425 °C. The use of W material in double CoFeB/MgO frames as a suitable metal spacer may enable the development of practical industrial STT-MRAM devices beyond a feature size of 20 nm
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